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STP22-0347 DA Engineering Report RFI Response Rev C
STRUCTURAL
CIVIL
ELECTRICAL
MECHANICAL
HYDRAULIC
FIRE
VERTICAL
TRANSPORT
SEISMIC
Ozcare Noosa
DA CIVIL ENGINEERING REPORT & STORMWATER MANAGEMENT PLAN
ENRICH ARCHITECTURE
STP22-0347
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Page 2
STP CONSULTANTS
Document Verification
Job Title Ozcare Noosa – DA Engineering Report
STP Project Reference STP22-0347
Client Reference 1907NOO
Document Status
Approved for Issue
Rev.
Issue Project Consultant
No.
Approved by Signature Date
Ken Miller
1 First Issue STP Consultants 11/03/2022
RPEQ 09053
Ken Miller
2 FINAL STP Consultants 08/11/2022
RPEQ 09053
Ken Miller
3 REVISION A STP Consultants 24/11/2022
RPEQ 09053
Ken Miller
4 REVISION B STP Consultants 23/03/2023
RPEQ 09053
Ken Miller
5 REVISION C STP Consultants 03/05/2023
RPEQ 09053
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STP CONSULTANTS
Contents
1. Introduction ........................................................................................................................................................3
2. Site Description ..................................................................................................................................................3
2.1 Easements..................................................................................................................................................3
2.2 Proposed Development .............................................................................................................................4
3. Stormwater Management Plan .........................................................................................................................5
3.1 Flood Studies..............................................................................................................................................5
3.2 Stormwater Detention................................................................................................................................5
3.3 Stormwater Quality ....................................................................................................................................5
3.4 Existing Stormwater Infrastructure...........................................................................................................5
3.5 Site Stormwater Drainage .........................................................................................................................5
3.6 Site Earthworks ..........................................................................................................................................5
4. Water Supply and Sewerage............................................................................................................................10
4.1 Water Connection ....................................................................................................................................10
4.2 Sewer Connection....................................................................................................................................10
5. Roadworks and Traffic Impact........................................................................................................................11
5.1 Parking and Access .................................................................................................................................11
5.2 Proposed Fire track & Construction Access ..........................................................................................11
6. Conclusions ......................................................................................................................................................11
7. Appendix A – Schematic Layouts ...................................................................................................................12
8. Appendix B – Typical Access Track Crossing................................................................................................17
9. Appendix C – Stormwater Quality Management Plan ...................................................................................20
9.1 Pollutants of Concern..............................................................................................................................21
9.2 Design Objectives for Water Management ............................................................................................21
9.3 Proposed Stormwater Treatment Train Analysis ..................................................................................22
9.4 Music Modelling.......................................................................................................................................22
Model Parameters....................................................................................................................................22
Rainfall & Runoff Parameters ..................................................................................................................23
Pollutant Generation ................................................................................................................................23
Results ......................................................................................................................................................23
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1. Introduction
Enrich Architecture has engaged STP Consultants to produce a Development Assessment Report for Engineering
Services, in support of an application for Material Change of Use over the site for an extension to an existing Aged
Care Facility. This report has been revised in partial response to Noosa Shire Council’s Further Advice Notice issued
on 25 January 2023, in particular, Items 4, 8, 9, 10, 11, 12 and 14.
This report will provide additional detail in the following areas:
Site earthworks
Stormwater management and flood risk
Stormwater quality
Water supply
Sewerage reticulation
Preliminary traffic impact
2. Site Description
The site is located at 100 Cooyar Street, Noosa Heads and described as Lot 9 on RP225312 with a land area of
2.5ha. The site is zoned Community Facilities under the Noosa Shire Council City Plan and is currently used as an
Aged Care Facility.
Figure 2.1 – Zoning and Locality Plan (NSC Mapping)
2.1 EASEMENTS
There is a single access easement A on SP197575, for an electrical sub-station, as shown in Figure 2.1 below.
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Emt A SP1975
75
Figure 2.2 – Existing access easements (Qld Globe)
2.2 PROPOSED DEVELOPMENT
The proposed development consists of demolition and reconstruction of accommodation wings, administration
building, and a community centre as depicted in Figure 2.3 below.
REFUSE COLLECTION &
GAS BOTTLE AREA
REFER TURNING PATHS
EXISTING TRACK CROSSING
STORMWATER OUTLET
SERVICE DELIVERY AREA
REFER TURNING PATHS
ADDITIONAL TRACK CROSSING
STORMWATER OUTLET
Figure 2.3 – Proposed site layout Stages 1, 2, 3A and 3B (Enrich Architecture)
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3. Stormwater Management Plan
3.1 FLOOD STUDIES
According to the Noosa Shire Council Flood Study, the site is not subject to flood inundation at the AEP 1% level.
3.2 STORMWATER DETENTION
Comparison of the impervious areas between the existing layout and the ultimate layout following completion of
Stage 3B, shows an overall increase from 12,370m2 (IF = 0.4952) to 12,374m2 (IF = 0.4954) or 0.03%. This change
is considered to be negligible and will not result in a measurable increase in site runoff. As this is the case, there
will be no requirement for on-site detention for the proposed development.
3.3 STORMWATER QUALITY
In accordance with the Assessment Benchmarks outlined in State Planning Policy, a Stormwater Quality
Management Plan will be required in order to reduce the impact of the proposed development on the quality of
stormwater discharged from the site. The site area is greater than 2,500m2 and the proposed development will
result in the net developed area being greater than 25%. A stand-alone Stormwater Quality Management Plan,
analysing the effect of the newly developed areas only, is included in Appendix C to this report.
3.4 EXISTING STORMWATER INFRASTRUCTURE
The site currently drains to the wetlands to the north-east, which is the Lawful Point of Discharge as illustrated in
the site survey in Figures 3.1 and 3.2 below.
3.5 SITE STORMWATER DRAINAGE
A preliminary stormwater drainage layout is illustrated in Figures 3.3 and 3.4. For the main development area, the
roofwater will discharge either directly to ground via splash pads or to roofwater inlet pits. The roofwater outlets
and the landscaped areas are to discharge directly to the open swales which will then outlet to the eastern reserve
area via the two proposed causeway structures.
Rock causeways are proposed where the stormwater drainage outlets from the site at the two locations indicated
in Figure 3.3. Detailed design drawings are included in Appendix B to this report. Catchment areas and runoff
calculations for the two major catchments are included in Figure 3.5 and Table 3.1 below.
The northern maintenance area (Figure 3.4) is a partial demolition and extension of the existing paved area, with a
consequent increase in impervious fraction for the area. Of the existing 249m2 impervious area, 73m2 is to be
demolished and be revegetated, with 176m2 to be retained. The area is to be extended with an additional 182m2 of
impervious pavement. The net impervious pavement area increases from 236m2 to 329m2. It is proposed to
discharge runoff from this area to a gravel soakage pit on the eastern boundary.
3.6 SITE EARTHWORKS
Existing site levels and grades are generally to be maintained. A minimal volume of fill may be required for building
pad works within strip footings. Minor excavation will be necessary for the creation of drainage swales and the
external fire track. A preliminary earthworks layout is shown in Figure 3.6.
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Figure 3.1 – Existing infrastructure - north (Bennett & Bennett)
Figure 3.2 – Existing infrastructure - south (Bennett & Bennett)
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Figure 3.3 – Proposed stormwater schematic layout (STP). Refer Appendix A.
Figure 3.4 – Proposed stormwater schematic layout - Maintenance area (STP). Refer Appendix A.
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C-01
C-
02
Figure 3.5 – Major stormwater catchment areas.
Time of Concentration = Roof travel time (4.6.5) + Channel flow (4.6.10)
Tc (C-01) = 5 + 5 = 10 min
Tc (C-02) = 5 + 10 = 15 min
Table 3.1 – Catchment runoff calculations
The proposed grassed swale will generally consist of a 5m wide section with a 1m base and side batters at 1:8 for
a maximum depth of 250mm. At a minimum grade of 0.25% (1 in 400), the swale will have a capacity of 0.422m3/s
at a maximum velocity of 0.56m/s.
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The rear access track will consist of a 5.0m wide gravel formation of 200mm crushed rock base over a trimmed
and compacted subgrade. The profile will consist of a 4% one-way crossfall, 4.0m wide with 0.5m shoulders,
designed to be free-draining. The two crossing points will be constructed as rock causeways for unobstructed
overland flow. Typical details are included in Appendix B.
Manning’s trapezoidal channel calculations are shown below, indicating a rock size in the range 30-50mm for the
calculated maximum velocity of 0.79m/s at the AEP 1% event.
Figure 3.6 – Proposed earthworks and fire track schematic layout (STP). Refer Appendix A.
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4. Water Supply and Sewerage
4.1 WATER CONNECTION
The new buildings will connect into the existing internal reticulation as illustrated in Figures 3.1 and 3.2 above. All
new and amended fixtures will be subject to a Plumbing and Drainage Application to Noosa Shire Council. It is
unlikely that the existing connection to the Unitywater infrastructure will require upgrading. This is located to the
north of the main entrance in Cooyar Road and fed by a crossing from the 150mm main located on the opposite
side.
4.2 SEWER CONNECTION
The new buildings will connect into the existing internal reticulation as illustrated in Figures 3.1 and 3.2 above. All
new and amended fixtures will be subject to a Plumbing and Drainage Application to Noosa Shire Council. It is
unlikely that the existing connection to the Unitywater infrastructure will require upgrading.
As illustrated in Figure 4.1, the site is traversed by existing Unitywater sewer infrastructure. Any construction within
5m of this 300mm trunk main will require approval from Unitywater under Queensland Development Code MP1.4.
Figure 4.1 – Existing sewer infrastructure (Unitywater)
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5. Roadworks and Traffic Impact
5.1 PARKING AND ACCESS
The access to the site will remain mostly unchanged as a result of this development. As there is no change to the
number of beds proposed, there is no additional demand for parking or impact on external traffic. Additional
parking and manoeuvring areas are proposed however, to provide better amenity and accessibility for current staff
and visitors. The turning paths shown below, indicate that sufficient area is available for all proposed vehicles
using the site.
Figure 5.1 – Refuse area and delivery area vehicle manoeuvres (Refer Appendix A).
5.2 PROPOSED FIRE TRACK & CONSTRUCTION ACCESS
The rear access track will be upgraded to a 5.0m wide gravel formation of 200mm crushed rock base over a
trimmed and compacted subgrade. The profile will consist of a 4% one-way crossfall (4.0m carriageway width
with 0.5m shoulders) designed to shed runoff without concentration of flow. The two crossing points will be
constructed as rock causeways. This will provide permanent access for fire monitoring purposes as well as
suitable access for construction vehicles. Typical details are included in Appendix B.
6. Conclusions
The proposed development is in complete compliance with Development Codes 9.3.4 Special Residential Code
and 9.4 Works Code.
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STP CONSULTANTS 7. Appendix A – Schematic Layouts Civil Engineering Report & Site Based Stormwater Management Plan | STP22-0347 12
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STP CONSULTANTS 8. Appendix B – Typical Access Track Crossing Civil Engineering Report & Site Based Stormwater Management Plan | STP22-0347 17
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STP CONSULTANTS 9. Appendix C – Stormwater Quality Management Plan Civil Engineering Report & Site Based Stormwater Management Plan | STP22-0347 20
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9.1 POLLUTANTS OF CONCERN
The South-East Queensland Stormwater Quality Guidelines provide guidance on the types of pollutants likely to be
generated from different developments. The Water Quality Objectives for Noosa are listed in Table 9.2. The
pollutants most likely to be of concern for Residential and Commercial developments are identified in Table 9.1
below.
Development Phase
Pollutant
Construction Operation
Litter
Sediment unlikely
Hydrocarbons (including oil and grease)
Toxic materials (e.g. cement slurry, asphalt primer, solvents) unlikely
pH altering substances (e.g. cement slurry and wash waters) unlikely
Oxygen demanding substances (organic and chemical matter) possibly unlikely
Nutrients (nitrogen and phosphorus)
Pathogens / Faecal coliforms (bacteria and viruses) possibly unlikely
Heavy metals (often associated with fine sediment unlikely unlikely
Surfactants (e.g. detergents from car washing) unlikely possibly
Thermal pollution (heat) unlikely unlikely
Table 9.1 – Pollutants Likely to be of Most Concern
9.2 DESIGN OBJECTIVES FOR WATER MANAGEMENT
The Environmental Protection (Water) Policy 1997 provides a framework for identifying environmental values and
associated water quality objectives; this framework is consistent with the efficient use of resources and best
practice environmental management and involves the community through consultation and consideration of
economic and social impact assessment. Environmental Values (EV) are a reflection of the qualities of a
catchment that the community believes to be important. As such, environmental values are established through
community consultation rather than through a scientific process. Once EV are established for a catchment, Water
Quality Objectives (WQO) can be defined, which are meant to protect these values.
While load based reduction targets focus on performance of a stormwater quality management system within the
urban footprint, concentration based WQO’s are concerned with median flow concentrations as they enter
downstream receiving water.
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Load Based Water Quality Objectives
Parameter Statistic
Reduction
Total Suspended Solids (TSS) Mean Range 80% Less than 5mg/L
Total Phosphorous (TP) Mean Range 60% Less than 0.01 to 0.05mg/L
Total Nitrogen (TN) Mean Range 45% Less than 0.2 to 0.5mg/L
PH Mean Range - Between 7 and 8
Greater than 80% saturation during
Dissolved Oxygen Mean -
daytime
Retention of litter greater than 50mm
Gross Pollutants - 90% for flows up to the 3-month ARI peak
flow
Retention of sediment coarser than
Coarse sediment - - 0.125mm for peak flows up to the ARI
3-month peak flow
Table 9.2 – Water Quality Objectives for South-East Queensland
9.3 PROPOSED STORMWATER TREATMENT TRAIN ANALYSIS
The proposed development site has sufficient area available to dedicate to stormwater treatment devices. Roof
water will discharge via downpipes directly to the in-ground stormwater. The landscaped areas and pavements
will discharge directly to field inlet pits or to overland flow. All grated field inlets will be fitted with filter baskets for
removal of gross pollutants. Treatment is undertaken within the grassed swales which then discharge to the
existing Lawful Points of Discharge to the north and east of the site.
9.4 MUSIC MODELLING
MODEL PARAMETERS
Input Data Used
Rainfall Station 40059 COOROY COMPOSITE
Rainfall Period 01/01/1973 – 31/12/1983
Mean Annual Rainfall (mm) 1600mm
Evapotranspiration 1629mm
Model Timestep 6 minutes
Rainfall Runoff Parameters* Commercial
Pollutant Parameters* Commercial (Split)
Table 9.3 – Basic MUSIC Model Parameters
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RAINFALL & RUNOFF PARAMETERS
Parameter Roof/ Road/Ground Level
Rainfall Threshold (mm/day) 1
Soil Storage Capacity (mm) 18
Soil Initial Storage (% of Capacity) 10
Field Capacity (mm) 80
Infiltration Capacity coefficient - a 243
Infiltration Capacity exponent - b 0.6
Initial Depth (mm) 50
Daily Recharge Rate (%) 0
Daily Baseflow Rate (%) 31
Daily Deep Seepage Rate (%) 0
Table 9.4 – Water by Design MUSIC Quantity Parameters for South-East Queensland (Commercial)
POLLUTANT GENERATION
In MUSIC, stormwater quality is characterized by event mean concentrations (EMC) for storm flows and base
flows. In this study, the EMC were adopted from the Water by Design MUSIC Modelling Guidelines. The
pollutants of concern that were assessed include total suspended solids (TSS), total phosphorous (TP) and
total nitrogen (TN). The quality of stormwater runoff is characterised by inputting event mean concentrations
(EMC) for storm flow and base flow conditions as well as the standard deviation of each EMC.
Pollutant concentrations are based on Commercial land use parameters.
TSS (log10 values) TP (log10 values) TN (log10 values)
Flow Type Surface Type
Mean Std Dev. Mean Std Dev. Mean Std Dev.
Baseflow Roof 0.00 0.00 0.00 0.00 0.00 0.00
Roads 0.78 0.39 -0.60 0.50 0.32 0.30
Ground level 0.78 0.39 -0.60 0.50 0.32 0.30
Stormflow Roof 1.30 0.38 -0.89 0.34 0.37 0.34
Roads 2.43 0.38 -0.30 0.34 0.37 0.34
Ground level 2.16 0.38 -0.39 0.34 0.37 0.34
Table 4.5 – Water by Design MUSIC Modelling Parameters - Commercial Split Catchment (SEQ)
RESULTS
The indicative layout of the MUSIC model and results are shown below in Figure 9.1 and Table 9.6.
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Figure 9.1 – MUSIC Model Treatment Train
Table 9.6 – MUSIC Modelling Results
As demonstrated, the proposed treatment train will reduce pollutant loadings to the extent specified
by the Noosa Shire Council Stormwater Quality Guidelines with the exception of Total Phosphorus
which achieves 97% of the target.
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